Psoriasis is a noncontagious disease that affects the skin and joints. The disease is accompanied by red scaly patches on the skin, called psoriatic plaques, which are areas of inflammation and excessive skin production. As many as 7.5 million Americans have psoriasis, according to the National Institutes of Health. It has been estimated that about 10 percent to 30 percent of people with psoriasis will also develop a joint disease known as psoriatic arthritis, which causes joint pain, stiffness and swelling.
Psoriasis is a chronic recurring condition, which can vary significantly in severity. Some sufferers exhibit minor localised patches of psoriatic plaques, while others have plaque overage over almost every area of the body. Fingernails and toenails are often affected.
The cause of psoriasis is not known, but it may have a genetic component. Stress, excessive alcohol consumption, and smoking have been known to aggravate the condition. In addition to the obvious physical manifestations, individuals with psoriasis may also suffer from depression and loss of self-esteem.
There are many topical medications that have been utilized to treat psoriasis. For example, vitamin D-3 (calcipotriene), coal tar, corticosteroids (e.g., clobetasol, fluocinolone, and betamethasone), tree bark extract (e.g., anthralin), and retinoids (e.g., tazarotene). Compositions for treating psoriasis that include both vitamin D compounds and corticosteroids have also been described (see U.S. Pat. No. 6,753,013). Combinations of vitamin D compounds and corticosteroids can be unstable, since the corticosteroids tend to favor acidic conditions, whereas vitamin D compounds are more stable in alkaline conditions. TACLONEX® topical ointment is a combination product, which includes both calcipotriene and betamethasone dipropionate, and is stabilized by a polyoxyalkylene ether-type solvent.